Support the Space for Life

Would you like to participate in the advancement of natural science and scientific culture? Get people interested in environmental issues? Become a member of the Space for Life Foundation and take part in its activities.

What is an insect?

Dorsal view: The elytra, or hardened forewings, of this firefly cover part of the thorax and abdomen.

Photo: Insectarium de Montréal (Mélanie Riverin)

Ventral view: Easily discerned are the head, the thorax (with legs) and the segmented abdomen.

Photo: Insectarium de Montréal (Mélanie Riverin)

The White Admiral seems to have only four legs. However, close observation of the butterfly reveals two atrophied front legs unsuitable for walking.

Photo: Insectarium de Montréal (Marjolaine Giroux)

The caterpillar of the Polyphemus Moth has three pairs of true legs on the front of the body. It is an insect, even if his body is not divided into three parts.

Photo: Insectarium de Montréal (René Limoges)

At the adult stage, insects’ bodies are divided into three parts: the head, thorax and abdomen. It has three pairs of legs and often has wings. If you keep these characteristics of insects in mind, it’s easy to tell them apart from other arthropods.

However, the insect world is full of exceptions – some species don’t have wings, others have no eyes… As well, an insect’s larval stage and its adult stage can be very different.

A strange way of breathing

Insects do not have a nose and lungs for breathing. Air enters through a series of small holes on the sides of their body called stigmata. Air circulates through their bodies via a network of rigid tubes called tracheas.

Free circulation

An insect’s heart is shaped like a long tube with tiny openings. Insect blood is called hemolymph. This liquid is often clear, yellowish or greenish, and circulates freely through the insect’s body. Insects do not have veins.